This may seem silly, but I use a combination of a solid mac desktop (upgraded a mac mini with SSD and 16GB ram), an iPad for taking to classes, and a cheap windows netbook. I do all my heavy work at my desktop, but most of my moving around time is with my iPad. the iPad doesn't have Flash (which is annoying) so sometimes I resort back to my netbook. I also use Chrome Remote desktop to get back into my mac from anywhere using the netbook.

Reasoning:
iPad is super light so I'm not lugging the laptop around all the time. iPad also has really awesome apps for studying. I also prefer reading papers and textbooks when I can get them on the iPad.

Netbook is cheap so if I drop it or something I'm not dead in the water.

I use the heck out of my 27 inch screen and love having a solid desktop which I can access via remote desktop anywhere.

Spendiness:
you could go with an android tablet and probably be able to remote desktop and flash without the use of the netbook. I just happen to go the iPad route.

I am in my last year at ASU Mechanical Engineering Program. The software that will need to be installed on your computer among other things is primarily Matlab and Solidworks. I know Matlab is compatible on most major operating systems but I am actually not sure about Solidworks being able to be on a non-windows machine. Matlab runs pretty good without a lot of computer power for the first few years worth of projects but can demand more depending project complexity. Solidworks had major efficiency improvements with 2013 version but still can be very demanding.

For price to power ratio PC will be more cost effective. If mobility around the dorm and school is a real important feature it might be worth it for you. To be transparent I have a tower at home and live off campus. The school has multiple labs with really nice capable machines with all the software you need so bring a flash drive and doing work at school is very possible. That is what I do. First floor of the Goldwater building and the Computer Commons have i5's and i7's and I have never waited for a computer.

Portability is key. As an engineering student you will spend the next four (or five years depending on your ability to pass classes the first go around) in Noble library. Ain't nobody got time for PCs and it's essential to always be able to carry your laptop around running Matlab or whatever will help you be most efficient in finishing your homework. Plus just think late nights up studying you can lay in bed with laptop resting on your legs and get some solid study time.

I got a laptop before coming to ASU, in retrospect I might have been better served by a desktop. More convenient, especially for shut-ins. If I had to do it over, I'd build a decent PC and buy a shitty used netbook on eBay for like $100.

I feel as though having a laptop in college is crucial, the added portability of a laptop is a definite plus. It allows you to study outside of your room, take your laptop to classes, and study in the library or just on the go. If you're looking into gaming (as I know many engineering students are), I'd recommend you get a gaming laptop (although not an Alienware, as those are pesky to lug around all day.)